Olive Oil Diet Curbs Strokes

Until now, evidence was weak that the Mediterranean diet reduced the risk of heart disease. But a New England Journal of Medicine study reveals startling new findings that will silence skeptics for good. WSJ's Andrea Petersen has the details on Lunch Break. Photo: AP.

By

Andrea Petersen

Updated Feb. 26, 2013 6:13 p.m. ET

A diet common in coastal areas of Southern Europe, particularly one with lots of olive oil and nuts, cuts the risk of stroke and other major cardiovascular problems by 30% among high-risk people, according to a new study.

Related Video

Your company already knows whether you've been going for regular medical checkups and getting your teeth cleaned. Now some employers or their insurance companies are monitoring what staffers eat and where they shop. MarketWatch's Christopher Noble reports. (Photo: Getty Images)

There's a large body of research linking a Mediterranean diet—one heavy on fruits, vegetables, fish and beans—to heart health. But this study, published Monday in the New England Journal of Medicine, is significant both for its size—it followed 7,447 people in Spain over almost 5 years—and its scientific rigor. Few previous studies have succeeded in proving a direct link between a diet and a reduction in life-threatening events like strokes, instead assessing the diet's impact only on weight loss or certain cardiovascular risk factors, like blood pressure or cholesterol.

ENLARGE

The study is "hugely important," says Steven Nissen, chairman of the department of cardiovascular medicine at the Cleveland Clinic, who was not involved in the study. Dr. Nissen notes that the preventive effect of the diet is similar to the effect of taking statins, the cholesterol-lowering drugs, which research has shown to reduce the risk of major cardiovascular events by about 25% to 30%. "What we can say to patients is this very palatable Mediterranean diet looks to be healthiest. I'm going to change my own diet; add some more olive oil, some more nuts."

The participants, who were between 55 and 80 years old, didn't have cardiovascular disease when they enrolled in the study, but were at high-risk for developing it because they had diabetes, were smokers, had high blood pressure, abnormal cholesterol, had strong family history of heart problems or were obese. Many were on medications to treat their risk factors: Almost half were taking drugs for high blood pressure and more than 40% took statins.

The participants were divided into three groups. Two groups were advised to follow a Mediterranean diet, which also encourages wine with meals and limits red meat, soft drinks and commercial baked goods. One of the Mediterranean diet groups was told to consume at least four tablespoons of olive oil per day. The other was told to eat 30 grams of nuts (walnuts, almonds and hazelnuts) every day. (The participants were given the olive oil and nuts.) The control group was told to follow a low-fat diet consisting of fruits, vegetables, low-fat dairy products, bread, pasta and fish. All participants could eat as much as they wanted and didn't receive any exercise advice. Many of the researchers have financial ties to the food and pharmaceutical industries.

ENLARGE

A diet common in coastal areas of Southern Europe, particularly one with lots of olive oil and nuts, cuts the risk of stroke and other major cardiovascular problems by 30% among high-risk people.
Getty Images

Participants in the Mediterranean diet groups had quarterly training sessions with dietitians and were given surveys to assess their adherence to the diet. Every year, they also had blood and urine tests to measure certain biomarkers to confirm their consumption of the extra olive oil and nuts. The researchers said that extra-virgin olive oil was used in the study because it contains more polyphenols, which have been shown to improve cholesterol levels, than refined olive oil.

Low-fat diet advocates point out that while the control group participants were advised to follow a low-fat diet, they didn't necessarily do so. Indeed, the researchers said that "changes in total fat were very small" during the course of the study among the participants in the control group.

Still, because the benefit demonstrated by the Mediterranean diet was so striking, the study was stopped early. Clinical trials are sometimes halted early to allow all participants to switch to a clearly beneficial treatment.

At the end of the study, 3.8% of the Mediterranean-diet-plus-olive-oil and 3.4% of the Mediterranean-diet-plus-nuts groups suffered a heart attack, stroke or death from cardiovascular disease. By comparison, 4.4% of members in the control group suffered this outcome. The differences in the risk of stroke were statistically significant. The differences in the risk of heart attack weren't, possibly because of the low incidence of heart attacks among people in the study, researchers said.

"In Spain, we are losing the Mediterranean diet," said Ramón Estruch, a professor at the University of Barcelona and a lead author of the study. He pointed to a need to tell people, "Remember what you learned at home from your grandmother and grandfather. It is really healthy."

This copy is for your personal, non-commercial use only. Distribution and use of this material are governed by our Subscriber Agreement and by copyright law. For non-personal use or to order multiple copies, please contact Dow Jones Reprints at 1-800-843-0008 or visit www.djreprints.com.